I. Field
The present invention relates generally to data communication, and more specifically to techniques for performing rate control for data transmission on multiple parallel channels in a multi-channel communication system.
II. Background
A multi-channel communication system utilizes multiple “parallel channels” for data transmission. These parallel channels may be formed in the time domain, frequency domain, spatial domain, or a combination thereof. For example, the multiple parallel channels may be formed by different time slots in a time division multiplex (TDM) communication system, different frequency subbands in a frequency division multiplex (FDM) communication system, different disjoint sets of subbands in an orthogonal frequency division multiplex (OFDM) communication system, or different spatial channels in a multiple-input multiple-output (MIMO) communication system. TDM, FDM, OFDM, and MIMO systems are described in further detail below.
The multiple parallel channels may experience different channel conditions (e.g., different fading, multipath, and interference effects) and may achieve different signal-to-noise ratios (SNRs). The SNR of a parallel channel determines its transrission capability, which is typically quantified by a particular data rate that may be reliably transmitted on the parallel channel. If the SNR varies from parallel channel to parallel channel, then the supported data rate would also vary from channel to channel. Moreover, since the channel conditions typically vary with time, the data rates supported by the multiple parallel channels also vary with time.
Rate control is a major challenge in a multi-channel communication system that experiences continually varying channel conditions. Rate control entails controlling the data rate of each of the multiple parallel channels based on the channel conditions. The goal of the rate control should be to maximize the overall throughput on the multiple parallel channels while meeting certain quality objectives, which may be quantified by a particular packet error rate (PER) or some other criterion.
There is therefore a need in the art for techniques to effectively perform rate control for multiple parallel channels having varying SNRs.